TriggerShims – The ExhaustNotes Blog

By Joe Berk

I should have known better. Before I tried good buddy Lance’s bolt shims (at TriggerShims.com), I was a bit skeptical even though another of Lance’s products had worked (and is still working) very well for me. I installed Lance’s cylinder shims on my Model 60 Smith and Wesson revolver a few years ago and they solved a lot of ills, including excess cylinder gap, difficulty in opening the cylinder, velocity loss, and double action misfires. The Model 60 is completely reliable now (I’ll include a link to that story at the end of this blog).

The above notwithstanding, though, I was still skeptical about bolt shims. I didn’t understand the concept of rimfire rifle bolt shimming, and that fueled my cynicism. I mean, on a bolt action rifle, what is there to shim?

I called Lance at TriggerShims and spoke with him. Lance said his customers tell him bolt shims work, but I wouldn’t know until I tried them. I was up for it. I had two rimfire rifles I felt should be more accurate: A Remington Custom Shop Model 504 and a CZ 452 Varmint model. The CZ would shoot moderately well off and on (it wasn’t consistent); the Remington was a major disappointment from the day I bought it. It was expensive and for something coming from Remington’s Custom Shop, I expected a lot more. The Custom Shop 504 rifle is beautiful, its walnut stock is fabulous, but its groups were poor.

The Concept

When you get a set of bolt shims from Lance, you get five in varying thicknesses. The shims are color coded so you don’t have to guess at what they are or measure them. The package looks like you see below.

A pack of TriggerShims’ bolt shims. Note the color coding on the shims. Five shims come in a package; the fifth one from the envelope you see above now resides in my Remington Model 504.

How Bolt Shims Work

Most rimfire bolt action rifles’ bolts are different than centerfire bolts. On a centerfire bolt, the bolt locks into the receiver at the front of the bolt. On most rimfire bolt action rifles, the bolt locks into the receiver at the bolt handle, the forward portion of the bolt extends forward to meet the rifle’s breech, and the bolt’s locking lug is integral to the bolt handle. Typically (as is the case on my CZ 452 and Remington 504), the forward portion of the bolt is actually two separate and concentric cylinders, with the forward part of the bolt able to move forward on the inner cylinder (i.e., closer to the chamber) if it is shimmed to do. You can see it in my Model 452 CZ bolt in the photos below.

The CZ 452 bolt disassembled. The arrow points to the 0.002-inch TriggerShims shim placed on the bolt shank.

Now consider headspace, the amount of clearance between the cartridge base and the bolt face. If there’s too much headspace, case separations can result when the brass case stretches during firing. Not enough headspace, and you can’t close the bolt. You might wonder: Why not simply have line-to-line contact in the chamber between the cartridge and the chamber, with zero headspace when the bolt is closed? That could work if you always shot with cartridge cases from the same manufacturer, there was no variation in the cartridge cases, there was no variability from rifle to rifle, you always fired your weapon at the same ambient temperature, and you always let it cool completely between shots. These qualifiers are unrealistic, so rifle manufacturers add clearance (i.e., headspace) so that the bolt can always close on any rifle they manufacture when using any kind of ammo meeting the cartridge’s external dimensional specifications at any reasonable temperature.

On a centerfire bolt action rifle, we can use tricks like neck sizing the case (instead of full length resizing the case) so that if that case was previously fired in the same rifle, a reloaded cartridge will have much less clearance between the cartridge case, the bolt face, and the chamber walls. This often works with a centerfire cartridge if, when reloading the cartridge, we only resize the case neck (that’s called neck sizing). Sometimes it’s an easy way to shrink groups (i.e., to make your reloaded ammo more accurate).

We don’t reload .22 ammo, though. So what can we do to eliminate unnecessary headspace? That’s where TriggerShims’ bolt shims enter the picture. The idea is that instead of increasing the length of the brass case to eliminate unnecessary headspace, we push the bolt face forward (toward the rifles’ chamber) to shrink the headspace. In the photo above, you can see where the TriggerShims bolt shim fits between the bolt handle and the bolt’s outer cylinder. When the bolt is assembled with the bolt shim installed, it looks like this:

The arrow points to the bolt shim. It pushes the bolt face forward 0.002 inches.

The bolt shim is visible from the bolt underside. Because the bolt locks with a lug on the bolt handle casting, the forward portion of the bolt sits further forward when the bolt shim is installed.

The package from TriggerShims contains five shims of different thicknesses, color coded by thickness. Lance doesn’t know how much shimming your bolt might need, and initially you don’t either. One approach is to go at this question as you would when developing a load for a centerfire rifle; i.e., trying different powders, powder charges, etc., except the sole independent variable is shim thickness. Here, the questions are how much excess headspace is there in your rifle, and how much should you remove to optimize accuracy?

The best approach to answering the above questions is to take the shims to the range, and with your preferred ammo, shoot groups with no shims, the 0.0015-inch shim, the 0.002-inch shim, the 0.003-inch shim, the 0.004-inch shim, and the 0.005-inch shim, and then select the shim that provides the greatest accuracy. Theoretically, if you switched ammo brands, you could repeat the process and find the best shim for the new ammo. It’s very clever.

Me? I’m lazy. I watched a bunch of YouTube videos describing the above and I decided I didn’t want to disassemble and then reassemble my bolt at the range, so I simply installed the 0.002-inch shim on both my CZ 452 Varmint and my Remington Custom Shop Model 504. (The Model 504 bolt shim installation is very similar to how it’s done on the CZ.)

The Results

Does it work? In a word, yes. I wouldn’t have believed it without trying it myself. I’m here to tell you the results are nothing short of amazing.

Remington Model 504

As I mentioned at the start of this blog, my Model 504 was a real disappointment. Yeah, it’s beautiful, with deep, lustrous bluing and gorgeous walnut.

My Custom Shop Model 504. It sure is pretty.

But the Model 504 didn’t group well with any ammo. That was a surprise, partly because of the rifle’s price, partly because of the Remington Custom Shop’s reputation for stellar performance, and partly because the rifle was glass bedded from the Custom Shop. I did my online research (ass backwards, as usual, after I bought the rifle) and I learned that Model 504s are known for lousy accuracy. I tried screwing around with relieving the bedding where it interfered with the barrel attaching screw, I tried different action screw torques, and I tried different ammo. Nothing worked. I thought I had been stuck with a beautiful rifle that was essentially a paperweight. Here are a couple of typical groups from the Model 504 at 50 yards with Eley Target ammo (which is good stuff) before I installed the bolt shim.

A Model 504 typical pre-bolt-shim-installation 5-shot group at 50 yards.

Another pre-bolt-installation group at 50 yards from the Model 504. Before installing the bolt shim, I would have considered this a good group from this rifle.

As you can see, they are what we in the engineering world would call lousy. The groups would vary, seldom going as low as that 1.041-inch group you above. Mostly they were awful.

I then installed a 0.002-inch trigger shim on the Model 504 and I tried it again. Wow! Look at this!

A dramatic and immediate improvement with the 0.002-inch bolt shim. This first group with the bolt shim installed was shocking. It got even better (see below).

The next group from the Model 504 with the bolt shim. I’m a believer.

When I saw those groups through the 12X Weaver scope on my Model 504, I couldn’t believe what I was seeing. In my mind, I could hear Lance’s calm voice in our recent telephone conversation telling me there’s no guarantees, but folks say they work. Indeed they do!

CZ452 Varmint

I was blown away by the Model 504’s improved accuracy with the addition of the 0.002-inch bolt shim, so I wanted to try it on the CZ.

The CZ has always shot better than the Model 504. Here’s a typical 10-shot group with the CZ452 before I installed the bolt shim:

I meant to shoot a 5-shot group before installing the bolt shim, but I shot 10 instead. It’s a typical group from the CZ before I installed the bolt shim.

What you see above is what the CZ would do at 50 yards with Eley Target ammo in my hands. Sometimes it would do a little better. Sometimes it would do a little worse. I’m not that great a shot; other people could probably do better. But it’s typical for me. I wanted it to do better.

The TriggerShims 0.002-inch bolt shim went into the CZ and again, my response was: Wow!

One little tiny 0.002-inch bolt shim and voila!

Someone once said only accurate rifles are interesting. These two rifles suddenly became much more interesting with the addition of TriggerShims bolt shims.

The Bottom Line

As the saying goes, your mileage may vary. But I’m convinced: Bolt shims work. I might be able to improve my groups even more if I experimented a bit with different shim thicknesses, but I’m more than pleased with what I saw after trying my simple and unscientific “install the 0.002-inch shim and see what happens” approach. This really is a great product. If you want to improve a bolt action .22 rifle’s accuracy, check out TriggerShims. You can thank me later.

Pretty Wood

People sometimes ask how I find guns with exceptional wood. It’s easy. I can’t pass a gun shop without stopping, and I spend a lot of time on gun forums. Every once in a while, I’ll see a rifle with walnut that speaks to me. The Model 504 you see here came from First Stop Guns (they’re in Rapid City, South Dakota) when Susie and I were out there touring that part of the country. I spotted the CZ 452 on a forum post and I sent a message to the owner asking if he would sell it to me. The first answer was no, but a year later the owner contacted me and asked if I was still interested. You know the answer to that one.

Pretty lumber indeed, and now they are both shooters. The CZ 452 is on the left; the Custom Shop Model 504 is on the right. You don’t often see .22 rifles with wood like this. For that matter, you don’t often see centerfire rifles with this kind of wood, either.

About that Model 60 cylinder shim story I mentioned…

Join our Facebook ExNotes page!

Never miss an ExNotes blog:

Help us keep the lights on:

Don’t forget: Visit our advertisers!

By Joe Berk

Wow, it’s March already. It seems like just a couple of days ago it was February. Seriously, though, the years are flying by. I had a bunch of things I wanted to mention, so this blog may meander a bit. Bear with me.

Baja John on the road to San Felipe back in 2005.

I got a note from Baja John yesterday. He’s down in San Felipe, which is not that big a stretch for him as he leaves down in Baja now. San Felipe celebrated their 100th anniversary this weekend and John wrote to tell me about it. Baja John, good buddy Marty, and I rode down there for San Felipe’s 80th anniversary, and if your Ph.D is in math, you know that means our ride was 20 years ago this past weekend. Those 20 years sure went by in a blur. It feels like that ride was maybe a couple of months ago.

John and yours truly two decades ago. I rode a Harley in those days. John rode a Virago. The BMW belonged to our friend Marty.

Man, I miss those Baja trips.

Speaking of time, I somehow made the Ball Watch email list. Their watches have a unique way of making the hands glow in the dark, which is kind of cool. I usually don’t find their style appealing, but Ball introduced a watch they call the Trainmaster a couple of years ago, and that one is beautiful. But at $2995 it’s not appealing enough (at least to me). I don’t need another watch. It sure is elegant, though.

The Ball Trainmaster. I would love to own one of these. It’s a GMT, too, one of my favorite watch types.

You may recall that several months ago we explained the origins of the expression, “Balls out.” That one means running flat out, and it is nontesticular in nature (it refers instead to a mechanical governor’s centrifugal balls being fully extended). It doesn’t have anything to do with Ball watches, either. But another expression, “on the Ball,” does. The official watch for railroads back in the 1800s was a Ball pocket watch (the same company that now makes the watch you see above), and if a train was running on schedule, it was said to be “on the Ball.”

Two Old Timers for $26 at Walmart! I already accidentally cut myself with the big one.

The pocketknife thing is in full swing. I thought I had just a few laying around in various spots in the house, so I decided to gather them up and put them all in one spot. I was a little bit embarrassed when I finished. I don’t need any more pocketknives. But that may not stop me. I have one more inbound, and I’ll probably stop after that. Or not. We’ll see.

More good stuff: I’ve had an old Savage 99 lever gun (chambered in 250 Savage) stashed away and neglected for several decades. Well, I finally dug it out a couple of months ago, and the neglect was obvious. It was rusty when I got it, but I let it get worse. Most of the rust is now off and it looks good. I bought some new 250-3000 brass cases and a set of Lee dies. I’m surprised I took this long to get around to the Savage, and I’m even more surprised at just how nice a cartridge the .250 Savage is.

A .250 Savage round in a Savage 99 rifle that is one year younger than me.

I haven’t finished the dialing in the load or the rifle, and I am already getting these kinds of results at 100 yards. The .250 Savage cartridge is a winner!

Another bit of misadventuring: I had a couple of old laptops that weren’t working and I’ve held off on tossing them for fear there might still be data on the hard drives. How do you wipe a hard drive so that whatever was there can’t be recovered? After a few minutes Googling the topic, it seems that the best way is to pull the hard drive and drill a few holes through the disk. Simply deleting the files or even using programs designed to eliminate whatever’s on there really doesn’t get the job done. I have a power drill, but I had a better idea. How about putting the hard drives behind a target and having at them with a .45?

Two guys getting blown away at the West End Gun Club. There was a laptop hard drive behind the head on each target.

ARX .45 ACP bullets meet hard drive. Yep, that worked.

Hard drives rendered unusable: Mission accomplished.

One more last item: You remember I told you about good buddy Lance and how well his end shake shims worked in my Model 60 snubbie. His company, TriggerShims.com, also makes bolt shims for .22 rifles I have two sets coming in for two of my .22 rifles, and I’m going to see how well they work.